SPEAKER SUGGESTS EXPLORING METHODS FOR WELDING PLASTICS

ATLANTA—Welding two or more plastic parts together often is cheaper than molding one complex part, but industry's technical knowledge of welding remains very limited, said Vijay Stokes, a 20-year veteran of GE's corporate research and development.

Stokes, who works at GE's engineering mechanics laboratory in Schenectady, N.Y., was the plenary speaker April 27 to kick off the first full day of Antec '98 in Atlanta's Infoforum meeting hall.

``Although we have had an array of welding methods that have been available for over 25 years, they still are not well-understood,'' said Stokes, who 10 years ago spearheaded the effort to form the Joining of Plastics and Composites Special Interest Group at the Society of Plastics Engineers.

In his morning speech, Stokes said that, although welded parts are becoming more common, welding remains a tiny part of plastics processing — and molders still believe molding a complete part in a single shot, instead of welding two parts together, is a noteworthy achievement.

Even so, large-load-bearing parts, such as car bumpers, already have benefited from plastics welding, he said.

Stokes said work is under way to vibration weld automotive intake manifolds, which now are made in one shot by a lost-core process.

Stokes reviewed several technologies for welding together plastic parts: thermal welding, including hot plate welding; friction methods, such as spin welding, vibration welding and ultrasonic welding; and electromagnetic welding, which includes a process that seals a special gasket inside the two parts.

Stokes holds 26 U.S. patents. He said the following areas need more research:

The impact performance of welded parts.

Long-term effects of residual stresses.

Fatigue performance of welds.

How environmental factors impact welds.

``No one is really addressing this, not the resin companies or the companies that design the equipment,'' he said.

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